I can't tell a whole lot, but it's more likely American, judging from the casualness with which the detectives carry guns. The clothing indicates late teens or early 20s to me, but I could be wrong about that. I'll watch some more and see if anything else leaps to the eye.
This is a bit of a long shot, but could it be "Hide and Seek, Detectives" from 1918? The IMDb page is
http://www.imdb.com/title/tt0009174
There's not a lot of information, but the two detectives seem to match the descriptions I could find for Heinie Conklin and Tom Kennedy. I couldn't find any pictures of either to verify that, though. The clothing and buildings seem to work well enough for 1918. The street scene, as seen from the top of the building, appears to have both cars and horse-drawn carts, which would also be consistent with the year.
Update: Trares, it looks like you're probably right. And here I was rabbiting on about clothing and horsecarts, as though I had a clue. Embarrassing.